The present invention relates to a functional unit comprising a self-supporting hollow stick or rod made up of a longitudinally shirred packaging tube, preferably a packaging tube based on fiber-reinforced cellulose hydrate, and a supporting container which envelopes the hollow stick leaving the stick cavity openings free. The supporting container is comprised of a single piece of a grid-like structured tubular supporting sheathing made of a plastic material, and star-shaped disc elements which are disposed at the ends of the sheath constituting the supporting container and serve to fix the sheath around the hollow stick.
The invention further relates to a process for the manufacture of the above-mentioned functional unit and to the use thereof in the production of sausages.
Meat preparations in the form of sausage emulsions filled into synthetic tubular casings are put onto the market in great quantities. The artificial sausage casings are composed either of a synthetic material or of cellulose hydrate tubes which are, preferably, fiber-reinforced.
In the production of sausages, tubes of the above-specified kind are used which have a length of, for example, 20 m. By means of conventional apparatus, these tubes are longitudinally gathered and simultaneously folded in a known manner into hollow cylindrical, self-supporting sticks which are open at both ends and are, at the same time or later, compressed in the direction of their longitudinal axis. This is known as shirring. Starting out from a tube length of 20 m, such self-supporting hollow sticks formed by shirring tubes have a length of about 40 cm.
When the packaging tube forming the hollow stick is to be filled with sausage emulsion, it is first closed at one of its ends and then the hollow stick is, with its open end forward, pushed onto the stuffing horn of a sausage filling machine. The sausage emulsion is then continuously and under pressure filled into the hollow stick, which is thereby unfolded according to the amount of sausage emulsion pressed into the tube.
Due to their manufacture, the hollow sticks have a certain dimensional stability or inherent rigidity, but they are sensitive to bending stresses and will easily break into two or more parts which are linked to one another by unfolded integral tube sections. Broken sticks are, however, practically useless.
The great mechanical stress to which the tube forming the hollow stick is subjected in the filling procedure makes it necessary to soak the hollow stick of cellulose hydrate tubing in water, prior to filling. During soaking, the tube absorbs water and swells and there is, therefore, a risk that the hollow stick undergoes a change of length and a reduction of its inherent rigidity. As a result, the stick can often no longer be used for its intended purpose.
There is a particularly great risk that the hollow stick may lose its original shape and dimensions upon handling, due to the above-mentioned influences, if the tubular casing forming the hollow stick has a relatively thick wall, for example, of 0.07 mm and a comparatively large inside diameter, for example, of 40 mm.
U.S. Pat. No. 4,013,099 proposes a method of overcoming the above-mentioned drawback, but this method has the disadvantage that, in the use of the known sheathed hollow stick, the inverted projecting ends of the support sheathing forming the supporting container cannot reliably be prevented from returning, in an undesired way, into their original position. Even an application of additional clamp ring elements which encompass the outsides of the inverted sheath ends does not suffice to hinder the projecting ends of the support sheathing from leaving their inverted position.